Threaded joint type connection for a drill in a hammer drill

ABSTRACT

In a hammer drill a threaded joint type engagement is provided between the drill and the drill socket. Preferably, the drill is threaded into the drill socket and the threaded engagement is continuously tightened and loosened during operation and can be easily disassembled for replacement of the drill. The drill is arranged in the socket so that the impact energy from the hammer drill is transmitted without affecting the interengaged connection of the parts.

United States Patent Chromy r THREADED JOINT TYPE CONNECTION FOR A DRILL IN A HAMMER DRILL lnventor:

Assignee:

Franz Chromy, Gisingen, Austria Hilti Aktiengesellschaft, Furstenlum, Liechtenstein Nov. 28, 1969 Schaan,

Filed:

Appl. No.:

Foreign Application Priority Data Dec. 2, 1968 Germany ..P l8 12 229.7

US. Cl. ..l75/388, 173/132, 175/405,

175/414 Int. Cl ..E21b 9/16, E21b 17/042 Field of Search ..l75/4l5, 403, 405, 389, 414, 175/92; 173/132, 131

Primary ExaminerMarvin A. Champion Assistant Examiner-Richard E. Favreau AttorneyMcGlew and Toren [5 7] ABSTRACT In a hammer drill a threaded joint type engagement is provided between the drill and the drill socket. Preferably, the drill is threaded into the drill socket and the threaded engagement is continuously tightened and loosened during operation and can be easily disassembled for replacement of the drill. The drill is arranged in the socket so that the impact energy from the hammer drill is transmitted without affecting the interengaged connection of the parts.

7 Claims, 6 Drawing Figures PATENTEDSEP 12 m2 SHEET 1 OF 2 VENT R FRHNZ CHROMY THREADED JOINT TYPE CONNECTION FOR A DRILL IN A I-IAMlVIER DRILL SUMMARY OF THE INVENTION The present invention is directed to the replaceable engagement of drills in the drill socket of a hammer drill and, more particularly, it is concerned with a threaded joint type engagement of the drill within the drill socket.

In drill hammers the drills must each have the same diameter drill shaft for fitting into the tool receiver independent of the diameter of the drill itself. Larger drills require a correspondingly larger drill shaft. Ac cording1y, the tool receiver of the drill hammer must be dimensioned to accept the range of drills employed. To be able to use drills of both small and large diameters, it is necessary to use a drill socket which has both a shaft for insertion into the tool receiver and a receiver or socket for the drill.

There are known drill sockets which have a receiving bore that tapers conically in the direction of the shaft of the drill socket. Similarly, the shaft of the drill to be inserted into the receiving bore is conically shaped so that the drill is held by the friction developed between the coinciding conical surfaces when the drill is inserted into thedrill socket.

Friction type joints or connections between the shaft of a drill and the bore of a drill socket have a number of disadvantages. A part of the impact energy transmitted from the hammer drill is converted into heat by the friction between the contacting conical surfaces. Due to the blows exerted by the hammer drill on the drill socket, the drill is driven into the drill socket so that it becomes difficult to remove and its replacement can be achieved only by considerable effort using a wedge and a hammer. Moreover, the interior conical surface on the drill socket and the exterior conical surface on the shaft of the drill must be formed very accurately in relationship to one another, otherwise, it is not possible to disengage the drill from the socket or the socket does not properly hold the drill in place. The production of such drills and drill sockets requires maximum precision with only small tolerances between the two with the result that production costs are increased.

Accordingly, it is the primary object of the present invention to overcome the disadvantages experienced in the past in securing drills within drill socketsand to provide a threaded joint type engagement between the two. Therefore, in accordance with the present invention, a screw or threaded joint is provided between the shaft of the drill and the bore in the drill socket. Such a joint assures a firm connection between the drill and drill socket during operation of the hammer drill and also provides easy disengagement of the drill from the socket. In this type of connection seizing of the drill within the drill socket is not possible because, though the joint is tightened by the circumferential force exerted on the drill, it is also loosened by the blows of the percussion piston in the hammer drill exerted on the drill socket. As a result, the impact energy exerted by the hammer drill can be transmitted almost completely to the working edge of the drill since the conversion of impact energy into friction energy is considerably less in this arrangement than in the previously known conically shaped joints. Another advantage in the present joint construction is that tolerance accuracy of the degree previously required is no longer necessary. Further, shorter drill shafts and shallower socket bores are both possible with the result that considerably less material is required. Because of these characteristics of the joint of the present invention the production costs are reduced as compared to the prior art.

Preferably, the screw joint has a multiple thread so that a rapid and safe connection can be obtained between the drill and the drill socket.

In accordance with the present invention, the drill socket is threaded, preferably with a round thread, and the shaft or extension on the drill which seats within the socket is provided with a corresponding thread. With such an arrangement the danger of damaging the threads on the drill and the drill socket is reduced.

In another preferred embodiment of the screw type joint, projections are provided along the circumferential periphery of the drill shaft and corresponding helically extending grooves are formed within the bore of the socket.

To provide for more rapid interconnection of the drill into the drill socket, the bore in the drill socket is provided, preferably, with grooves extending parallel to its longitudinal axis.

In one embodiment of the invention the threaded extension or shaft on the drill has a diameter which is equal to or greater than the diameter of the drill proper and its length is such that it can be screwed into the bore in the drill socket until its end face contacts the bottom of the bore. In such a joint construction, it is possible to screw small drills, where the thread diameter is greater than the drill diameter, until the end face of the extension on the drill contacts the bottom of the bore in the drill socket, so that the impact energy is transmitted to the end face of the extension and not to the threads along its lateral surface. Moreover, it is also possible to screw a crown drill onto the extension of the drill and to use the small drill as a centering drill.

In still another embodiment of the invention, the threaded extension of the drill has a diameter which is smaller than that of the drill and its length is less than the depth of the bore in the drill socket. In this arrangement, the blows from the hammer drill are transmitted through the drill socket to'an annular shoulder formed on the drill at the point from which the extension projects from the drill. Accordingly, the impact energy is transmitted from the end face of the drill socket to the annular shoulder on the drill and not through the threads interconnecting the drill and drill socket.

It is preferable for the end of the extension on the drill and the bottom of the bore of the drill socket to be coplanar, so that the transmission of impact energy to the drill is improved.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference should be had to the accompanying drawing and descriptive matter in which there are illustrated preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawing:

FIG. 1 is a side view, partly in section, of a drill connected within a drill socket in accordance with the present invention and with a drill hammer represented schematically in phantom;

FIG. 2 is a view, similar to FIG. 1 illustrating another embodiment of the connection of a drill within a drill socket in accordance with the present invention;

FIG. 3 is a view similar to FIG. 2, which shows still another embodiment of the connection of a drill into a drill socket in accordance with the present invention with theaddition of a crown drill mounted on the drill;

FIG. 4 is a partial view, partly in section, of another embodiment of DETAILED DESCRIPTION OF THE INVENTION FIG. 5 is a view, partly in section, of a drill socket;

and

FIG. 6is a partial view of a drill arranged for engagementwithin the drill socket in FIG. 5.

,In FIG. 1,'a hammer drill 1 shown in phantom, has a tool receiver 2 at one end and contains a percussion piston 3. Positioned within the tool receiver 2 is a drill socket 4. At one end the drill socket 4 has an insert shaft 4a which extends into the hammer drill for operative contact with the percussion piston 3. Inthe opposite end of the drill socket 4 a bore 40 having a female circular thread 4b is provided. A drill 6 having a male circular thread 6a on an extension or shaft at one end is threaded into'the drill socket bore 40 until its end face 6b contacts the bottom surface 4d of the bore. The outside diameter of the male thread 6a is greater than the diameter of the bit portion of the drill 6.

When the hammer drill 1 is operated and the drill 6 is placed in contact with the material to be drilled, the interconnected drill socket 4 and drill 6 are driven in the direction of rotation by the tool receiver 2. Due to the rotational action the drill 6 is screwed more tightly into the-bore 40 because of the resistance developed at the cuttingedge of the drill. However, because of the action of the percussion piston 3 onthe end of the shaft 4a of the drill socket 4 which is transmitted through the bottom surface 4d of thebore 40 to the end face 6b of the drill extension, the screw joint between the drill and the drill socket is loosened somewhat. This tightening and loosening process is repeated continuously during the operation of the hammer drill. When operation is completed, the drill 6 can be easily removed from the drill socket 4 if the socket is pressed against the tool receiver by means of an auxiliary tool and the drill hammer is started up. Since the drill is not in contact with any surface, there is no tendency for a tightening action between the drill and drill socket, however, the hammering action of the percussion piston 3 will loosen the threaded engagement for easy removal.

In FIG. 2, as distinguished from the arrangement in FIG. 1, a drill 8 is provided on which the diameter of the bit portion of the drill is greater than the diameter of its male thread 8a on the extension which projects from the bit portion. As a result of this construction, an annular surface or shoulder 8b is formed in a plane transverse to the longitudinal direction of the drill. Additionally, the length of the threaded portion 8a of the drill 8 is less than the depth of the bore 40 in the drill socket 4, with the result that the blows exerted on the drill socket are transmitted to the annular shoulder 8b on the drill from the corresponding end face of the drill socket. As indicated in FIG. 2, the male thread 8a on the drill 8 is interrupted by a longitudinal groove which extends in parallel relationship to the longitudinal axis of the bore 4c and acts in the manner of a bayonet lock. With this construction, the rapid exchange of drills within the drill socket is possible.

In FIG. 3, a drill 10, similar to that shown in FIG. 1, is provided with an elongated extension containing a male thread 10a with a crown drill ll threaded onto a portion of the thread 10a. The threaded extension of the drill is seated at its end face 10b against the base 4d of the bore in the drill socket 4 while the end face of the drill socket containing the bore contacts the end surface 110 of the crown drill. In efiect, the transmission of the action of the percussion piston in FIG. 3 is a combination of the actions described by FIGS. 1 and 2. The rotational action provided by the tool receiver 2 is transmitted to the drill 10 from the base surface 4d of the bore to the end face 10b of the drill while the action from the socket 4 to the crown drill 11 is transmitted across the end face of the socket to the end surface 1 1a of the crown drill. As with the other embodiments, in the arrangement in FIG. 3, the transmission of the action of the percussion piston is obtained without damage to the thread 4b in the bore and the thread 10a on the drill.

In FIG. 4 a multiple female thread 46 is formed in the socket 4 and a multiple male thread 6a is formed on the end of the drill 6 which seats within the socket.

In FIG. 5 the socket 4 has a helical groove 4e and in FIG. 6 the end of the drill has a projection 8d which fits into the helical groove 4e.

I claim:

1. A drilling device comprising a hammer drill having a tool receiver opening therein, a percussion piston positioned within said hammer drill, a drill socket comprising a shaft on one end thereof for operative engagement within the tool receiver opening in said hammer drill and a socket bore in the other end thereof, a drill arranged to be operatively secured within said socket bore, wherein the improvement comprises engagement means formed within said socket bore, an extension formed on the end of said drill to be secured within said socket bore, said extension having a diameter at least equal to the diameter of said drill and having a length sufficient for its transverse end face to contact the bottom surface in said socket bore, engagement means fonned on said extension, and said extension arranged to fit within said socket bore with said engagement means thereon rotated into interlocking engagement with said engagement means in said socket bore.

2. A drilling device, as set forth in claim 1, wherein said engagement means in said socket bore comprises a multiple female thread and said engagement means on said drill extension comprises a multiple male thread.

3. A drilling device, as set forth in claim 1, wherein said engagement means on said drill extension comprises at least one projection formed on the circumferential periphery thereof and said engagement means in said socket bore comprises at least one helically extending groove formed in the circumferential periphery of said socket bore for receiving said projection on said drill extension.

4. A drilling device, as set forth in claim 1, wherein the end face of said drill extension and the bottom surface of said socket bore are coplanar.

5. A drilling device, as set forth in claim 1, wherein said drill extension has a diameter at least equal to the diameter of said drill and has a length greater than the depth of said socket bore so that when the end face of said extension contacts the bottom surface in said bore a portion of its threaded circumferential periphery extends outwardly from the end face of said socket containing said bore, a crown drill having a diameter greater than the diameter of said drill is threaded onto the portion of said drill extension projecting from said socket, and the end surface of said crown drill into which said extension is threaded is in contacting engagement with the end face of said socket containing said bore, whereby the action of said percussion piston is transferred to the end face of the extension of said drill from the bottom surface of said bore and to the end surface of said crown drill from the end face of said drill socket.

6. A drilling device, as set forth in claim 1, wherein said engagement means in said socket bore comprises a circular female thread and said engagement means on said drill extension comprises a circular male thread.

7. A drilling device, as set forth in claim 6, wherein at least one longitudinally extending groove is formed on the circumferential periphery of said drill extension and said groove extends in the axial direction of said drill across said circular threads formed thereon, and at least one longitudinally extending groove is formed in and extends in the axial direction of said socket bore traversing the female thread in said socket bore. 

1. A drilling device comprising a hammer drill having a tool receiver opening therein, a percussion piston positioned within said hammer drill, a drill socket comprising a shaft on one end thereof for operative engagement within the tool receiver opening in said hammer drill and a socket bore in the other end thereof, a drill arranged to be operatively secured within said socket bore, wherein the improvement comprises engagement means formed within said socket bore, an extension formed on the end of said drill to be secured within said socket bore, said extension having a diameter at least equal to the diameter of said drill and having a length sufficient for its transverse end face to contact the bottom surface in said socket bore, engagement means formed on said extension, and said extension arranged to fit within said socket bore with said engagement means thereon rotated into interlocking engagement with said engagement means in said socket bore.
 2. A drilling device, as set forth in claim 1, wherein said engagement means in said socket bore comprises a multiple female thread and said engagement means on said drill extension comprises a multiple male thread.
 3. A drilling device, as set forth in claim 1, wherein said engagement means on said drill extension comprises at least one projection formed on the circumferential periphery thereof and said engagement means in said socket bore comprises at least one helically extending groove formed in the circumferential periphery of said socket bore for receiving said projection on said drill extension.
 4. A drilling device, as set forth in claim 1, wherein the end face of said drill extension and the bottom surface of said socket bore are coplanar.
 5. A drilling device, as set forth in claim 1, wherein said drill extension has a diameter at least equal to the diameter of said drill and has a length greater than the depth of said socket bore so that when the end face of said extension contacts the bottom surface in said bore a portion of its threaded circumferential periphery extends outwardly from the end face of said socket containing said bore, a crown drill having a diameter greater than the diameter of said drill is threaded onto the portion of said drill extension projecting from said socket, and the end surface of said crown drill into which said extension is threaded is in contacting engagement with the end face of said socket containing said bore, whereby the action of said percussion piston is transferred to the end face of the extension of said drill from the bottom surface of said bore and to the end surface of said crown drill from the end face of said drill socket.
 6. A drilling device, as set forth in claim 1, wherein said engagement means in said socket bore comprises a circular female thread and said engagement means oN said drill extension comprises a circular male thread.
 7. A drilling device, as set forth in claim 6, wherein at least one longitudinally extending groove is formed on the circumferential periphery of said drill extension and said groove extends in the axial direction of said drill across said circular threads formed thereon, and at least one longitudinally extending groove is formed in and extends in the axial direction of said socket bore traversing the female thread in said socket bore. 